Techniques and systems for continuous-flow plasma enhanced atomic layer deposition (PEALD)

ABSTRACT

Techniques are disclosed for methods and apparatuses for performing continuous-flow plasma enhanced atomic layer deposition (PEALD). Plasma gas, containing one or more component gases, is continuously flowed to a planar inductive coupled plasma source attached at an upper end of a cylindrical chamber. Plasma is separated from the ALD volume surrounding a wafer/substrate in the lower end of the chamber by a combination of a grounded metal plate and a ceramic plate. Each plate has a number of mutually aligned holes. The ceramic plate has holes with a diameter less than 2 Debye lengths and has a large aspect ratio. This prevents damaging plasma flux from entering the ALD volume into which a gaseous metal precursor is also pulsed. The self-limiting ALD reaction involving the heated substrate, the excited neutrals from the plasma gas, and the metal precursor produce an ultra-uniform, high quality film on the wafer. A batch configuration to simultaneously coat multiple wafers is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority from now allowedU.S. patent application Ser. No. 15/458,642 filed on Mar. 14, 2017 andwhich is incorporated by reference herein in its entirety. Thisapplication is also related to and being co-filed on the same day asanother U.S. patent application entitled “Techniques and systems forcontinuous-flow plasma enhanced atomic layer deposition (PEALD)” bypresent inventor Birol Kuyel, and which application is also incorporatedby reference herein in its entirety.

FIELD OF THE INVENTION

This invention relates generally to atomic layer deposition (ALD) andmore specifically to continuous-flow ALD for depositing ultra-uniformatomically sized films/layers on a substrate.

BACKGROUND ART

Atomic layer deposition (ALD) is a special type of chemical vapordeposition (CVD) technique. ALD utilizes a sequential exposure ofgaseous reactants for the deposition of atomically sized thin films. Thereactants are often metal precursors consisting of organometallicliquids or solids used in the chemistry by vaporizing under vacuumand/or heat conditions. The reactants are introduced as a series ofsequential, non-overlapping pulses. In each of these pulses, thereactant molecules react with a substrate or wafer surface in aself-limiting way. Consequently, the reaction ceases once all thereactive sites on the wafer/substrate surface are consumed. Between thetwo pulses, a purge step is applied to remove the excess reactants andbyproducts from the process chamber. Using ALD, it is possible to growmaterials uniformly and with high precision on arbitrarily complex andlarge substrates. Some examples of films produced using ALD are SiO2,Si3N4, Ga2O3, GaN, Al2O3, AlN, etc.

The timing diagram of a typical prior art system is shown in FIG. 1.FIG. 1 shows two series of alternating pulses PA and PB of two reactantsA and B. The two pulses correspond to time periods T_(A) and T_(B)respectively, which includes a dosing time and any additional wait/purgetime required to pump out excess reactant and/or reaction products. Thisadditional wait/purge time for reactants A and B is indicated by w_(A)and w_(B) in FIG. 1. Therefore, the corresponding dosing times forreactants A and B are T_(A)-w_(A) and T_(B)-w_(B) respectively.

The cycle-time of such a prior art system is equal to T_(A)+T_(B) asshown in FIG. 1, consisting of a dose-purge-dose-purge sequence. Thecycle is repeated as many times as needed to obtain a film of thedesired thickness as required for a given application or recipe. In aplasma enhanced/assisted ALD (PEALD/PAALD) system, a plasma is used forreactant activation in order to trigger the self-limiting reaction onthe heated substrate. In contrast, in a thermal ALD system, hightemperature is used for facilitating the reaction.

There are many different techniques for performing ALD in the prior art.U.S. Pat. No. 7,314,835 to Ishizaka, discloses a method for depositing afilm on a substrate using a plasma enhanced atomic layer deposition(PEALD) process. The method includes disposing the substrate in aprocess chamber configured to facilitate the PEALD process. A firstprocess material is introduced within the process chamber, and a secondprocess material is introduced within the process. Radio Frequency (RF)power of more than 600 Watts (W) is coupled to the process chamberduring the introduction of the second process material. This results inthe generation of a plasma that accelerates a reduction reaction betweenthe first and second process materials at a surface of the substrate.The film is formed on the substrate by alternatingly introducing thefirst process material and the second process material.

U.S. Pat. No. 7,341,959 to Brcka also discloses a method for depositinga film on a substrate using a plasma enhanced atomic layer deposition(PEALD) process. The method includes disposing the substrate in aprocess chamber configured to facilitate the PEALD process. The processchamber includes a substrate zone proximate to the substrate and aperipheral zone proximate to a peripheral edge of the substrate. Themethod also includes introducing a first process material and a secondprocess material within the process chamber and coupling RF power to theprocess chamber during the introduction of the second process material.This results in the generation of a plasma that facilitates a reductionreaction between the first and the second process materials at a surfaceof the substrate.

Furthermore, RF power is coupled to a process electrode to generate asubstrate zone plasma in the substrate zone that ionizes contaminantssubstantially in a region of the substrate. RF power to a peripheralelectrode generates a peripheral zone plasma in the peripheral zonehaving a characteristic different from the substrate zone plasma. As aresult, the ionized contaminants are transported from the substrate zoneto the peripheral zone in the process chamber.

U.S. Patent Publication No. 2017/0016114 A1 to Becker discloses a gasdeposition chamber. The chamber includes a volume expanding top portionand a substantially constant volume cylindrical middle portion andoptionally a volume reducing lower portion. An aerodynamically shapedsubstrate support chuck is disposed inside the gas deposition chamberwith a substrate support surface positioned in the cylindrical middleportion. The top portion reduces gas flow velocity. The aerodynamicshape of the substrate support chuck reduces drag and promotes laminarflow over the substrate support surface. The lower portion increases gasflow velocity after the substrate support surface. The gas depositionchamber is configurable to 200 millimeter diameter semiconductor wafersusing ALD and or PEALD cooling cycles. A coating method includesexpanding process gases inside the deposition chamber prior to theprocess gas reaching a substrate surface. The method further includescompressing the process gases inside the deposition chamber after theprocess gas has flowed passed the substrate being coated.

U.S. Patent Publication No. 2012/0141676 A1 to Sershen teaches an ALDcoating system. The system includes a fixed gas manifold disposed over amoving substrate with a coating surface of the substrate facingprecursor orifice plate. A gas control system delivers gas or vaporprecursors and inert gas into the fixed gas manifold which directs inputgases onto a coating surface of the moving substrate. The gas controlsystem includes a blower interfaced with the gas manifold which drawsgas through the gas manifold to remove unused precursors. Also removedare inert gas and any reaction byproduct from the coating surface. Thegas manifold is configured to segregate precursor gases at the coatingsurface to prevent the mixing of dissimilar precursors. The gas manifoldmay also segregate unused precursor gases in the exhaust system so thatthe unused precursors can be recovered and reused.

U.S. Pat. No. 8,940,646 to Chandrasekharan discloses methods ofdepositing layers of material on multiple semiconductor substrates atmultiple processing stations within one or more reaction chambers. Themethods include dosing a first substrate with film precursor at a firstprocessing station and dosing a second substrate with film precursor ata second processing station. This is done with precursor flowing from acommon source such that the timing of the dosing is staggered. In otherwords, the first substrate is dosed during a first dosing phase duringwhich the second substrate is not substantially dosed, and the secondsubstrate is dosed during a second dosing phase during which the firstsubstrate is not substantially dosed. Also disclosed are apparatuseshaving multiple processing stations contained within one or morereaction chambers. Further disclosed is a controller with machinereadable instructions for staggering the dosing of first and secondsubstrates at first and second processing stations.

U.S. Pat. No. 9,343,296 to LaVoie discloses methods of forming SiC/SiCNfilm layers on surfaces of semiconductor substrates. The methods includeintroducing a silicon-containing film-precursor and an organometallicligand transfer reagent into a processing chamber. This results inadsorbing the silicon-containing film-precursor, the organometallicligand transfer reagent, or both onto a surface of a semiconductorsubstrate such that either or both form an adsorption-limited layer. Themethods also include reacting the silicon-containing film-precursor withthe organometallic ligand transfer reagent, after either or both haveformed the adsorption-limited layer. The reaction results in the formingof the film layer. In other variations, a byproduct is also formed whichcontains substantially all of the metal of the organometallic ligandtransfer reagent. The methods include removal of the byproduct from theprocessing chamber. Also disclosed are corresponding semiconductorprocessing apparatuses for forming SiC/SiCN film layers.

U.S. Patent Publication No. 2011/0003087 A1 to Soininen discloses areaction chamber of a reactor for coating or treating a substrate by anALD process. This is accomplished by exposing the substrate toalternately repeated surface reactions of two or more gas-phasereactants. The reaction chamber is configured to generate capacitivelycoupled plasma and comprises a reaction space within the reactionchamber. It also comprises a first inlet to guide gases into the chamberand an outlet to lead gases out of the chamber. The reaction chamber isconfigured to lead the two or more reactants into the reaction chamber.This is done such that the two or more reactants may flow through thereaction space across the substrate in a direction essentially parallelto the inner surface of the lower wall.

Non-Patent Literature (NPL) reference of “Plasma-Assisted Atomic LayerDeposition Al2O3 at Room Temperature” by Tommi O. Kaariainen dated 2009teaches a design of plasma source used for PEALD of Al2O3 films at roomtemperature. In their reactor, the plasma is generated by capacitivecoupling and directly in the deposition chamber adjacent to thesubstrate. However, it can be separated from it by a grid to reduce theion bombardment while maintaining the flow of radicals directly to thesubstrate surface.

During the ALD cycle, a mixture of nitrogen and argon is introduced intothe reactor to act as a purge gas between precursor pulses and tofacilitate the generation of a plasma during the plasma cycle.Sequential exposures of TriMethylAluminum (TMA) and excited O2precursors are used to deposit Al₂O₃ films on Si(100) substrates. Aplasma discharge is activated during the oxygen gas pulse to formradicals in the reactor space. The experiments show that the growth rateof the film increased with increasing plasma power and with increasingO2 pulse length before saturating at higher power and longer O2 pulselength. Their growth rate saturated at the level of 1.78 Angstrom (Å)per cycle.

U.S. Pat. No. 4,282,67 to Kuyel teaches a method and system forgenerating plasma using an RF-excited radial-flow, cylindrical plasmarector. The reactor includes a toroidal waveguide of rectangularcross-section connected to a microwave source. One of the reactivespecies of the plasma is flowed through the waveguide and ispre-ionized. The design permits independent control over the activationof both reactive species.

It is believed that widespread adoption of ALD technology for a varietyof promising industrial applications is predicated upon obtaining a filmthickness that is extremely uniform across the substrate and has verylittle or no hydrogen content. It is also important to reduce thecycle-time for the production of the film so that operational throughputcan be increased. Such an increased throughput would result in reducedcosts and other economies of scale. Furthermore, in traditional ALDsystems, Ammonia (NH3) is used for nitridation. NH3, being a corrosivechemical, incurs a high downstream cost of abatement as known by thoseskilled in the art.

The prior art cited above fails to accomplish these goals. Morespecifically, the prior art is ineffective at producing extremelyuniform films across the substrate surface with short cycle-times. Thatis because the high energy plasma flux is able to enter from the plasmachamber of typical prior art designs into the ALD volume around thesubstrate. Such prior art designs may use a showerhead (Chandrasekharan,LaVoie, Soininen) or a grid (Kaariainen) to separate the plasma from thesubstrate. The plasma is also sometimes pulsed to minimize exposure tothe substrate or to reduce the energy of the plasma ions/flux.

In any case, the result is that high energy plasma flux still manages toenter the ALD volume and gets into contact with the substrate. Thisresults in the damaging of the substrate surface and deterioration ofthe deposited film quality. Furthermore, the cycle-times in typicaldesigns cannot be significantly reduced. As a result, the prior art isunable to satisfy the very high quality and uniformity, low cost andhigh throughput requirements of many industrial applications.

OBJECTS OF THE INVENTION

In view of the shortcomings of the prior art, it is an object of thepresent invention to provide methods and apparatuses/systems forperforming ALD with high quality/uniformity of films, fast cycle-timesand low cost of operation.

It is another object of the invention to produce such highquality/uniformity films by preventing the flow of damaging plasma fluxfrom entering into the ALD volume.

It is still another object of the invention to significantly reduce theALD cycle-times as compared to traditional ALD systems.

It is yet another object of the invention to have a continuous-flow ofplasma gases into the chamber throughout the deposition process.

Still other objects and advantages of the invention will become apparentupon reading the detailed description in conjunction with the drawingfigures.

SUMMARY OF THE INVENTION

The objects and advantages of the invention are secured by methods ofsystems for performing continuous-flow atomic layer deposition (ALD).Although the present teachings support both plasma enhanced ALD (PEALD)as well as thermal ALD processes, special attention is paid to PEALD.This is because of the remarkably uniform films with little or nohydrogen content produced by PEALD. Furthermore, instant PEALDtechniques do not require ammonia (NH3) for nitridation, so expensivedownstream ammonia abatement activities are also avoided.

In the instant design, PEALD is carried out inside a chamber, at the oneend of which a substrate/wafer is placed above a platen which is heatedby a platen heater. Preferably, the platen heater heats the platen andthe substrate by resistive heating. The platen heater thus heats thesubstrate to a desired temperature. At the other end of the chamber isaffixed a preferably planar, inductively coupled plasma (ICP) source.Gas A or plasma gas is supplied to the planar ICP source by gas lines attwo laterally opposite gas feedthrough points from above the ICP source.In a distinguishing aspect of the technology, the plasma gas iscontinually/continuously flowed to the ICP source throughout thedeposition process.

Consequently, the plasma from the plasma gas or gas A is alsocontinuously generated in the instant continuous-flow PEALD design. Theplasma is generated below a quartz plate of the ICP source in thechamber. In another innovative aspect, the plasma is isolated from thesubstrate by a combination of a grounded metal plate and a ceramic plateaffixed in the chamber between the ICP source and the substrate. Thegrounded metal plate and the ceramic plate have a number of holes, suchthat each hole of one plate is perfectly aligned with a correspondinghole of the other plate.

The diameter of the holes in the metal plate is preferably ⅛ inches.However, the number of holes is far lesser than a typical denseshowerhead design of the traditional art. In comparison, thecorresponding holes of the ceramic plate are much smaller, preferablyless than two Debye lengths of the plasma. The plasma field is shortedby the grounded metal plate. But the excited radicals, terminated by themetal plate, pass through its holes as neutral atoms/molecules.

The excited neutrals then pass through the small ceramic plate holes toreach the ALD volume around the substrate. In yet another distinguishingaspect, the high energy plasma flux consisting of plasma ions andelectrons is prevented from entering the ALD volume by the ceramic platewhile only the excited neutrals pass through. This is only possiblebecause of the above mentioned design of the ceramic plate holes havingdiameter less than two Debye lengths.

The excited/activated neutrals thus reaching the ALD volume are alwayspresent around the substrate, in contrast to the typical ALD systemswhere only one reactant is present in the ALD volume at a given time. Apulse of a gas B is also passed into the ALD volume, preferably frombelow the substrate. Preferably, gas B is a metal precursor on a carriergas. In the ALD volume, the excited neutrals, the metal precursor andthe heated substrate react in a self-limiting manner. In a surprisingaspect of the design, a layer of atomically sized film is produced evenwith the continuous presence of one of the reactants (the excitedneutrals from the plasma). In this manner, remarkably uniform thickness,high quality films can be deposited/coated on the substrate surface.

As many pulses of gas B may be passed in as many ALD cycles as desiredto incur a required thickness of the deposited film. In a highlypreferred embodiment, the chamber comprises an upper portion and a lowerportion that can close to pneumatically seal the chamber. In anotherembodiment, gas A is a mixture of more than one component gases orchemical species. In yet another embodiment, gas B is also a mixture ofcomponent gases or chemical species. One of such component gases in gasB may be a carrier gas that is used to carry a reactant or precursorwith insufficient vapor pressure to reach the chamber.

Preferably, gas A comprises one or more of nitrogen, argon, oxygen andhydrogen. Preferably, gas B comprises a metal precursor and the filmdeposited is that of an oxide or a nitride of a metal. Preferably, theprecursor is of a metal such as aluminum (Al), gallium (Ga), silicon(Si), zinc (Zn), hafnium, etc. and carried on an appropriate carriergas. The carrier gas may be nitrogen (N2) or argon (Ar).

Preferably, the deposited film is one of AlN, Al2O3, GaN, Ga2O3, SiO2,Si3N4, ZnO, Zn3N2, HfO2, etc. Preferably the transit distance that theexcited neutrals travel in the chamber towards the substrate is lessthan 1 centimeter, significantly less than the traditional art. Thetransit distance is defined as the vertical distance from the uppersurface of the metal plate to the imaginary horizontal plane equidistantbetween the lower surface of the ceramic plate and the top of thesubstrate. Such a short transit distance is only possible because of thevery compact instant design. The system can also operate in pure thermalALD mode without requiring plasma.

Preferably, gas A is flowed to the planar ICP source substantiallyvertically with respect to the substrate. In contrast, gas B ispreferably flowed substantially horizontally with respect to thesubstrate. Very advantageously, the cycle-time of the ALD process asresult of the instant design is reduced to the duration of time betweentwo consecutive pulses of gas B. This is a significantperformance/throughput improvement over the prior art. That is becausein traditional art, each reactant is pulsed alternately and thecycle-time is equal to the time duration between two consecutive plusesof a reactant, including an intervening pulse of the other reactant.Also, since gas A is always present in the chamber, no separate purgecycle is needed in the present design.

As many pulses of gas B are sent to the chamber as needed to obtain afilm of a desired thickness. More specifically, as many ALD cycles areperformed as needed to obtain a film of a desired thickness. Duringthese cycles, one or more of the component gases or chemical species ofgas A and/or gas B may be changed during the execution of the recipe.This may be needed if films of different compounds need to be depositedin a single recipe. In such an embodiment, a purge cycle may need to beperformed before gas species are altered.

In a highly preferred embodiment, a load-lock mechanism is used toprevent oxidation of the finished/coated substrate. After the filmdeposition is complete, the load-lock mechanism, working in conjunctionwith a lift assembly of the platen heater, removes the hot substratefrom the chamber. It does so by virtue of an arm and an end effector tobring the hot substrate from the chamber into a pneumatically sealedload-lock compartment containing inert nitrogen (N2). The hot substrateis allowed to cool off in that inert environment before being exposed toenvironmental oxygen.

A batch version of the present PEALD design is also disclosed. In theinstant batch PEALD version, there are a number of substrate modulesvertically stacked inside a batch chamber. Each substrate module has aheated substrate at the bottom. The plasma is produced from gas A asbefore, but by a remote plasma source. Preferably, the remote plasmasource is inductive. At or near the remote plasma source is a plasmafilter module containing the metal plate with holes and ceramic platewith its holes of the earlier single-wafer embodiments.

Thus, the plasma from the remote plasma source is terminated by themetal plate of the plasma filter module. However, the excited/activatedneutrals pass through the metal plate holes and the ceramic plate holesof the plasma filter module. The excited neutrals from the plasma arethen fed into the batch chamber using normal tubing traveling up to adistance of preferably half a meter. The excited neutrals are then fedinto the ALD volumes of the substrate modules directly above the heatedsubstrates.

Another gas B is also flowed to the batch chamber. As before, gas Btypically comprises a gaseous metal precursor on a suitable carrier gas.Gas B is passed through the walls of the batch chamber and preferablydelivered directly above the heated substrates in the substrate modules.As in the case of single-wafer embodiments, the excited neutrals of gasA, gas B and the heated substrate react in a self-limiting fashioninside each substrate module. The result is an atomically sized film ofa remarkably uniform thickness deposited simultaneously on all thesubstrates in the batch chamber. As many ALD cycles may be run asdesired in order to obtain films of the required thickness.

Clearly, the system and methods of the invention find many advantageousembodiments. The details of the invention, including its preferredembodiments, are presented in the below detailed description withreference to the appended drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 illustrates a timing diagram of a typical ALD system of the priorart with cycle-time equal to the sum of durations T_(A) and T_(B)corresponding to two reactant pulses PA and PB respectively.

FIG. 2 is a perspective view of the chamber of a continuous-flow plasmaenhanced atomic layer deposition (PEALD) system according to thisdisclosure.

FIG. 3 is a top/plan view of only the bottom portion of the chamber ofFIG. 2.

FIG. 4 is a view of the platen heater, its lift assembly and itselectrical connections from the embodiments illustrated in FIG. 2-3.

FIG. 5 is an illustration of the instant innovative design of thegrounded metal plate with holes, and a ceramic plate with itscorresponding holes for preventing the flow of damaging plasma flux intothe ALD volume.

FIG. 6 is a cross-sectional view of the chamber of FIG. 2-3 along withadditional componentry required for an ALD system according to theinstant techniques.

FIG. 7 illustrates the timing diagram of the present ALD design ascompared to the timing diagram of prior art of FIG. 1, with cycle-timeequal to duration T corresponding to one reactant/precursor pulse PB.

FIG. 8 is a schematic diagram of the gas supply system for the PEALDtechniques disclosed in these teachings.

FIG. 9 is a variation of FIG. 8 providing support for thermal ALD.

FIG. 10 is an isometric view of a load-lock mechanism/assemblyinterfaced with the continuous-flow PEALD chamber of the presentteachings.

FIG. 11 is a detailed view of the load-lock mechanism/assembly of FIG.10 showing its internal components.

FIG. 12 shows in a flowchart form the steps required to carry out anexemplary embodiment of the continuous-flow plasma enhanced ALD (PEALD)techniques presently disclosed.

FIG. 13 shows a screenshot from the control software used tocontrol/manipulate the instant ALD system design for executing a recipe.

FIG. 14 shows a screenshot of the control software of the instant designfrom an actual recipe depositing a GaN film using GaCl3 as theprecursor.

FIG. 15 is a schematic diagram of a batch embodiment for performingcontinuous-flow PEALD on a batch of wafers according to the instantteachings.

DETAILED DESCRIPTION

The figures and the following description relate to preferredembodiments of the present invention by way of illustration only.

It should be noted that from the following discussion, alternativeembodiments of the structures and methods disclosed herein will bereadily recognized as viable alternatives that may be employed withoutdeparting from the principles of the claimed invention.

Reference will now be made in detail to several embodiments of thepresent invention(s), examples of which are illustrated in theaccompanying figures. It is noted that wherever practicable, similar orlike reference numbers may be used in the figures and may indicatesimilar or like functionality. The figures depict embodiments of thepresent invention for purposes of illustration only. One skilled in theart will readily recognize from the following description thatalternative embodiments of the structures and methods illustrated hereinmay be employed without departing from the principles of the inventiondescribed herein.

The present invention will be best understood by first reviewing achamber assembly or simply a chamber 100 of a continuous-flow plasmaenhanced atomic layer deposition (PEALD) system according to the presentteachings as illustrated in FIG. 2. It will be taught later in thisdisclosure that the instant principles support both PEALD as well asthermal ALD. However, there are several detailed PEALD embodimentsdisclosed below. This is because of the remarkably uniform filmsproduced with short cycle-times by the instant PEALD design.Furthermore, the PEALD techniques do not require ammonia (NH3) orhydrazine for nitridation, so the films have little or no hydrogencontent while expensive downstream abatement activities are alsoavoided.

FIG. 2 shows a perspective view of chamber 100. In the preferredembodiment, chamber 100 of the instant continuous-flow PEALD designcomprises an upper or top section or portion 102 and a lower or bottomsection or portion 120. There is a substrate/wafer surface or asubstrate/wafer sample or simply a substrate or a wafer or a sample 140in lower portion 120 on which deposition or coating of atomically sizedlayers is performed. Typically, the substrate is a silicon substrate.Sometimes the immediate volume inside chamber 100 surrounding thesubstrate is also referred to as the ALD volume or the process volume.Substrate 140 is placed on top of a heated platen (not shown) and isindicated in FIG. 2 by a dashed line. This is because it is present onthe inside of lower portion 120 below metal plate 122A and a ceramicplate (not shown). Both the platen heater and the ceramic plate will befurther discussed in detail below.

There is a planar inductively coupled plasma (ICP) source 104A attachedto top portion 102 at its far or distal end from lower portion 120.Planar ICP source 104A has a ducting or tubing or line 106A to carryplasma gas(es) to plasma source 104A at two laterally opposite gasfeedthrough points 106B and 106C as shown. According to a distinguishingaspect of the instant technology, a ground or grounded metal plate 122Awhose significance will be taught further below, is also affixed orattached to or integrated with chamber 100. In the embodiment shown inFIG. 2 it is affixed in lower/bottom portion 120.

However, in alternative embodiments metal plate 122A may be affixedright in between upper/top portion 102 and lower/bottom portion 120 orin upper/top portion 102. It should be noted that although the belowembodiments employ an inductively coupled plasma (ICP) source 104A, thepresent design may also accommodate a capacitively coupled plasma (CCP)source. Plasma flux from a CCP source may be more energetic. If thismore energetic plasma flux were to enter the ALD volume, it would causepinhole defects on the substrate surface, thus damaging the filmuniformity. Furthermore, the increased sputtering around the holes ofmetal plate 122A from the more energetic plasma may contaminate thedeposited film. Henceforth, an ICP source is preferred over a CCP sourcein the present design. The holes of metal plate 122A will be discussedin much more detail further below.

The preferred embodiment in FIG. 2 also shows a chamber lift 108 and abase plate 190 on which chamber or chamber assembly 100 is mounted.Further shown are ducting/lines 126A required to carry the plasmagas(es) to chamber 100 as will be taught further below. It should benoted that in FIG. 2, top portion 102 and bottom portion 120 of chamber100 are shown ajar to delineate their components on the inside. Ofcourse, the ALD process is carried out once the two portions are closedtogether with a snug and airtight fit to seal chamber 100.

A snug and airtight fit between upper section/portion 102 and lowersection/portion 120 is accorded by an O-ring 130 as shown in FIG. 3.FIG. 3 shows in a top/plan view only bottom portion 120 with top portion102 of chamber 100 removed for illustrative purposes. When top portion102 (not shown in FIG. 3) is pressed and locked against O-ring 130, anairtight seal between portions 102, 120 is achieved as required tomaintain the sealed conditions for the ALD process.

We may refer to the sealed state of chamber 100 as a substantiallysealed state in order to represent the range of vacuum conditionsrequired to carry out the operation of the ALD system. The vacuumconditions are preferably obtained by a combination of a backing pumpand a turbomolecular pump to be discussed further below. As a result,the system is able to achieve a pressure of about 10⁻⁶ Torr in chamber100 after 20 minutes of a pump down operation, and a pressure of about5*10⁻⁷ Torr in a clean, cold system after an overnight pump downoperation. Preferably, the operational pressure in chamber 100 rangesfrom 50 millitorrs to a few hundred millitorrs. As will be discussedthat preferably, during the self-limiting ALD reaction, the pressure inthe ALD volume around substrate 140 in lower portion 120 is kept at 0.27Torr or below.

FIG. 3 also shows three smaller O-rings around three stainless steellines of which only one O-ring and one line are indicated by referencenumerals 124 and 126A respectively for clarity. The purpose of O-rings124 is to seal the flow of gases in ducting/lines 126A. Lines 126A areconfigured to come from underneath and through base plate 190 (see FIG.2). They then enter into wall 128 of lower portion 120 at its side atgas ports/feeds 126B shown in the rear perspective view of chamber 100in the upper right hand corner of FIG. 2. In the rear perspective viewof chamber 100 shown in FIG. 2 within dotted-and-dashed lines, only someof the components are marked by reference numerals for clarity ofillustration and to avoid clutter. Lines 126A then travel upwards at aright-angle to O-rings 124 through wall 128 of lower portion 120 andinto top portion 102 when portions 102, 120 are in a closed position(also see FIG. 3).

Alternatively, lines 126A can come out from underneath baseplate 190 andthen directly enter wall 128 of lower portion 120, and then verticallyupwards to O-rings 124. In any case, lines 126A surrounded by O-rings124 at the interface of portions 102, 120 then come outside to the sideof upper portion 102 as a single line 106A. Line 106A comes out viaports/feeds 126C shown in the rear perspective view of chamber 100 inFIG. 2. Note that the embodiment of FIG. 2 shows only one such line 106Acoming out from upper portion 102. That is because all three lines 126A(also see FIG. 3) entering top portion 102 are allowed to mix togetherbefore coming out as a single line 106A.

In other embodiments, one or more of lines 126A may be allowed to enterdirectly into the inside of upper portion 102 through its internalsidewall and then to planar ICP source 104A without ever coming outside.Still in other embodiments, all three of lines 126A may come out to theside of upper portion 102 as three unmixed individual lines 106A thatmay feed into ICP source either from the side or from the top at one ormore gas feedthroughs. The skilled reader will recognize the manydifferent gas supply configurations available for practicing the instantteachings. As already noted, line 106A eventually feeds into ICP source104A from the top as two gas feedthroughs 106B, 106C shown in theembodiment of FIG. 2.

The gases flowing via lines 126A from lower portion 120 to upper portion102 may include reactant gases, plasma gasses, purge gases, or othertypes of gases as required by a given application or process recipe. Aswill be taught below, that even though the ALD system being explainedcan support the use of purge gases, a distinguishing aspect of thepresent technology is that it does not require a purge cycle. In thisdisclosure, by the term purge cycle we mean the step in which an inertgas, referred to as a purge gas, is passed through the ALD volume and/orthe plasma volume for a length of time. The length of the purge cycle ischosen to cleanse the volume(s) of existing reactants and/or thereaction products. This leads to an overall lengthening of cycle-timeand reduction in system throughput.

As will be discussed, that in the present design also, there is acertain wait time after a precursor pulse. During this time, thepressure in the chamber, specifically the ALD volume, decayssubstantially to the background level. Also during this time, any excessprecursor and/or reaction products can be pumped out or purged, beforenext precursor pulse is sent. However, since plasma gas(es) are alwaysflowing, a complete purge cycle using a purge gas and requiring a pumpdown and flushing/purging of the plasma chamber is avoided, resulting insignificantly shorter cycle-times than traditional systems.

The gases flow through stainless steel gas lines 126A around whichO-rings 124 are provided where upper portion 102 and lower portion 120close together. The above mechanism allows top and bottom portions 102,120 respectively to separate from each other without requiring flexibletubing to bring gasses to top portion 102. As a result, top chamber 102can be pneumatically lifted (manually or otherwise) using chamber lift108 while still allowing gases to flow from bottom portion 120 to topportion 102 when the two portions are in a closed position. As will beappreciated by those skilled in the art, that the use of stainless steellines of the above design provides for a higher reliability thanflexible tubing, and the pneumatic lift design provides for a userfriendly system operation.

As already hinted above, chamber 100 also has a heating mechanism forheating substrate surface 140 in bottom portion 120. Specifically, aplaten heater 142 as shown in FIG. 4 and constructed out of stainlesssteel is used for this purpose. Platen heater is a sealed unit thatmounts to baseplate 190 through a CF Flange (not shown). Note thatsample lift 143A of platen heater lift assembly is shown in FIG. 4 inthe raised position. However, lift 143A is normally in its depressedposition and below or leveled with its top or working surface on whichsubstrate 140 is placed during the ALD process. Heater 142 is capable ofheating substrate 140 (see FIG. 2) to any desired temperature.Preferably, heater 142 can heat substrate 140 up to 500° C. as requiredto carry out the self-limiting reaction for forming a uniform thicknessfilm as will be taught below.

In the preferred embodiment, heater 142 utilizes resistive heating. Itis designed to concentrate and maintain heat uniformly on its upper orworking surface on which substrate 140 is placed, while minimizing heatloss at its interface to baseplate 190. Advantageously, the temperatureis kept stable via a proportional-integral-derivative (PID) controller,such as one available from OMEGA. FIG. 4 also shows electricalconnections 144 underneath baseplate 190 to power heater 142. As aresult, platen heater 142 heats its top working surface/platen on whichsubstrate 140 is placed (also see FIG. 2 and associated explanation).

The heating ensues once platen heater 142 is electrically powered oractivated. As shown in FIG. 4, platen heater 142 also includes a liftassembly 143A-C used in transferring substrate samples from theload-lock mechanism. The working of lift assembly 143A-C and thelock-lock mechanism will be explained in detail later in thisspecification. In alternative embodiments, platen heater 142 may utilizeinductive heating, Infrared (IR) heating, or other means to heat its topworking surface or platen to heat the wafer/substrate. Inductive heatingis typically suitable for applications requiring very high temperaturesof the substrate, near 1000° C.

In addition, lower portion 120 is also independently heated by one ormore cartridge heaters to a temperature below that of substrate 140. Thepurpose of cartridge heater(s) is to heat the interior walls of lowerportion 120 and therefore to avoid condensation on these walls. One withskill in the art will readily understand the use of such cartridgeheater(s) and they are not explicitly shown in the drawing figures forclarity.

Let us now take a look at a cross sectional view of chamber 100 shown inFIG. 6 to further understand its internal components. FIG. 6 showsplanar ICP source 104A, its Radio Frequency (RF) inductive antenna/coil104B and a quartz plate 104E directly below antenna 104B. Sometimes thevolume surrounding the plasma in chamber 100 is also referred to as theplasma volume. In the embodiment shown in FIG. 2 and FIG. 6, the plasmavolume is contained below quartz plate 104E and above metal plate 122Awhen upper portion 102 and lower portion 120 are in a closed position.

It should be remarked that quartz plate 104E acts as the sealingcomponent of planar ICP source 104A while its RF coil/antenna stays atatmospheric pressure. An air cooling fan 104D is also provided as shown.In alternative embodiments, a water cooling mechanism can be used tokeep the system from overheating. The figure also shows metal plate 122Aand ceramic plate 123A underneath metal plate 122A as introducedearlier. Also shown are gas feeding lines 126A, platen heater 142,chamber lift 108, and plasma gas feeding line 106A from earlierteachings.

Further shown in FIG. 6 is a plasma viewport 146. Also shown areseparate reactant/precursor feeding lines 127 and 129 towards thefrontal part of lower portion 120. Diametrically across the chamber frominputs 127 and 129 is a vacuum port (not shown), which in combinationwith vacuum pumps discussed below, allows for removal of any unwantedgases from around substrate 140. These may include excess precursor andunwanted reaction byproducts.

FIG. 6 further shows some other componentry of the overall ALD system ofthe instant technology of which chamber 100 is a part. This preferablyincludes a turbomolecular pump 192 hinted above, an ALD filter housing196 and an exhaust pipe 198 driven by a backing pump (not shown) tosuction the gases out of chamber 100. Filter housing 196 preferably usesa large area heated filter before turbomolecular pump 192 for depositingunused precursor on a replaceable filter heated with a cartridge heater(not shown). The filter can then be periodically replaced during theoperation of the system. It should be remarked that FIG. 6 shows top andbottom portions 102, 120 of chamber 100 in an ajar position to delineateinternal components. It is understood that the ALD process taught hereincan only commence when these portions are closed/locked to obtain asealed state of chamber 100 per above teachings.

Referring back to FIG. 3, metal plate 122A has a number of holes 122B.Note that for clarity only one of the holes of metal plate 122A isdesignated by reference numeral 122B. According to an innovative aspectof the present design, holes 122B are far fewer in number than a typicaldense showerhead design available in the art. Without being limited by aspecific theory, the reason for this is that the present design does notneed uniform plasma flux over a large area for forming its uniform filmon substrate 140. Differently put, the gas flow pattern does not affectthe film uniformity. ALD process being self-limiting, a single atomiclayer can grow laterally until the surface of substrate 140 is coveredwith one uniform atomic layer.

Thus, the design can use sparsely distributed holes 122B as compared totraditional art, which in turn allows it to maintain higher pressure inthe plasma volume than in the ALD volume. This consequently preventsprecursor gas from diffusing to the plasma volume and depositing.Therefore, in the present design, quartz plate 104E does not accumulatedeposits in the present design. In a variation, instead of quartz, plate104E is made of alumina. The advantage of quartz is that one can see theplasma when looking down at ICP source 104A from above. Underneath metalplate 122A is a ceramic metal plate 123A as shown in FIG. 5 and alsoindicated earlier in the cross-sectional view of chamber 100 in FIG. 6.Referring to FIG. 5, ceramic plate 123A also has holes 123Bcorresponding to each hole 122B of metal plate 122A.

In another innovative aspect of the instant design, holes 123B ofceramic plate 123A have a diameter less than 2 Debye lengths of theplasma generated in chamber 100. However, holes 122B of metal plate 122Aare bigger and of a size more reminiscent of a typical shower headdesign. Preferably the diameter of metal plate holes 122B is about 0.125inches. Furthermore, metal plate 122A and ceramic plate 123A of theinstant design are attached to chamber 100 in alignment, such that eachhole 122B of grounded metal plate 122A is perfectly aligned with itscorresponding counterpart hole 123B of ceramic plate 123A.

According to the main aspects of the instant techniques, platen heater142 is used to heat substrate 140 (see FIG. 2, FIG. 4 and FIG. 6) to adesired temperature required to carry out the above mentionedself-limiting reaction. While chamber 100 is sealed per above teachings,a plasma gas or gas A is flowed/passed/introduced continuously to planarICP source 104A. We refer to the plasma gas as gas A in order todistinguish it from precursor gas or gas B introduced from below inchamber 100 and to be later explained. Per above explanation of O-rings124, after having been carried via lines 126A through wall 128 of bottomportion 102 and to top portion 102, gas A is eventually delivered toplasma source 104A via gas feedthroughs 106B-C on a continuous basis(see FIG. 2 and FIG. 6).

In contrast to traditional art, the plasma is continuously produced andpresent in chamber 100, specifically in the plasma volume, throughoutthe ALD process. Gas A or the plasma gas may consist of a singlechemical specie or it can be a mixture of different chemical/gasspecies. In the latter case, as already explained above, the gases mixinside lines 126A, 106A before being delivered via laterally oppositegas feedthroughs 106B-C to plasma source 104A as shown in FIG. 2.

Plasma source 104A is preferably powered by a 13.56 Mega Hertz RadioFrequency (RF) generator, such as 1213 W 1 kW RF Generator working withan AIT-600-10 auto-tuner both available from T&C Power Conversion, Inc.Alternatively, a 600 Watt RF generator with an auto tuner from any othersupplier may be used. FIG. 6 also shows an RF input port 104C to whichan RF cable (not shown) is connected from the RF power supply (notshown) to ICP source 104A. Also shown is a cooling fan 104D to preventoverheating of the plasma volume, and consequently that of entirechamber 100.

The plasma gas(es) are generally supplied from high pressurereservoir(s) or tank(s) via respective mass flow controllers (MFC) andassociated valves. The MFC's may or may not be digital. In the preferredembodiment, the plasma gas or gas A consists of a mixture of nitrogen N2and argon Ar, or a mixture of oxygen O2 and Ar, or a mixture of hydrogen(H2) and N2. Conveniently, a plasma viewport 146 is also provided in thesystem as shown in FIG. 2-3 and FIG. 6 to visually monitor the plasmaduring system operation as needed.

Because of the presence of grounded metal plate 122A which is at groundpotential and at a short distance below quartz plate 104E of ICP source104A, the plasma is rapidly terminated or shorted or quenched. However,the activated or excited neutrals (radicals terminated by metal plate122A) of gas A still pass through holes 122B of metal plate 122A andcorresponding smaller holes 123B of ceramic plate 123A (see FIG. 2-3 andFIG. 5-6). The excited neutrals from the plasma thus enter the ALDvolume around substrate 140 in bottom portion 120. The instant designthus results in a rapid quenching or “killing” of the plasma.

The transit distance is defined as the vertical distance from the uppersurface of metal plate 122A to the imaginary horizontal planeequidistant between the lower surface of ceramic plate 123A and the topof substrate 140. It is the distance that the neutrals travel when theyleave the plasma in the plasma volume to the approximate location wherethey undergo the ALD reaction in the ALD volume. As compared totraditional systems this transit distance of the instant design is muchshorter, and preferably less than 1 centimeter.

Traditional systems require upper plasma volumes of their chambershaving lengths of approximately 40 centimeters. In these systems, theplasma volume has to be large to assure the decay of plasma before gasmolecules arrive at the substrate. This large plasma volume intraditional systems then has to be pumped down or flushed/purged betweencycles resulting in long cycle-times. In contrast, the instant design ismuch more compact, with the plasma volume having a very short length.Specifically, the length of the plasma volume is the distance betweenthe lower surface of quartz plate 104E and the upper surface of metalplate 122A. This length of the instant plasma volume is preferablyapproximately of 1 inch. This compact design, combined with thecontinuous-flow of plasma gas(es) without requiring a purge of theplasma volume, results in substantially lower cycle-times than intraditional art.

For ease of understanding, the transit distance d and the length of theplasma volume 1 of the instant design are illustrated in thedot-and-dashed outlined box in the upper right hand corner of FIG. 6.Note that d and 1 in the above box are not necessarily drawn to scale,and are illustrated for showing their relationships with respect to therest of the elements of the instant design, namely quartz plate 104E,metal plate 122A, ceramic plate 123A and substrate 140.

Due to the combination of plates 122A, 123A and their holes 122B, 123Brespectively, the plasma ions and electrons, sometimes referred to asthe ion flux, do not penetrate the small holes 123B of ceramic plate123A. They thus do not damage substrate 140 as in traditional systems.In order to accomplish this, in yet another innovative aspect, holes123B of ceramic plate 123A are specifically designed to have a diameterless than 2 Debye lengths. As a result, the plasma flux is preventedfrom entering the ALD volume to the extent that its damaging effects onthe substrate are negligible for most applications.

Referring to FIG. 6, another reactant/reagent referred to as gas B isalso introduced into chamber 100, specifically into its bottom portion120. Gas B is introduced as a pulse into the ALD volume where heatedsubstrate 140 resides. Gas B reactant/reagent is pulsed through gas line127 from below where substrate is placed above the working surface ofplaten heater 142.

Preferably, the plasma gas or gas A is flowed to planar ICP source 104Asubstantially vertically with respect to substrate 140. This isaccomplished by feeding gas A to ICP source 104A by vertical gasfeedthroughs 106A-B as already explained, and the fact that excitedradicals of gas A pass down vertically as neutrals via holes 122B, 123Btowards substrate 140 (also see FIG. 2 and FIG. 5). In contrast, gas Bis preferably flowed substantially horizontally with respect tosubstrate 140. This is accomplished by line 127 which feeds gas B frombelow substrate 140 such that gas B horizontally surrounds the surfaceof substrate 140.

In other embodiments, reactant/precursor feeding line 127 may beprovided from a side, or at another appropriate location in chamber 100,as long as it feeds in below ceramic plate 123A. This is required tokeep the precursor gas in the ALD volume where the ALD reaction with thesubstrate and the excited neutrals from the plasma gas needs to takeplace. Of course, the ALD reaction can only commence when top and bottomportions 102, 120 are sealed and not in the ajar position shown in FIG.6 for delineating internal componentry.

Sometimes, the plasma gas or gas A may also be referred to as simply thereactant while gas B may also be referred to as the precursor. This isbecause gas B is typically used as a metal precursor (on an appropriatecarrier gas), that is utilized in the self-limiting ALD reaction fordepositing a compound of the metal on the substrate. Thus, while allprecursors are reactants, not all reactants are precursors. In thisdisclosure, we will use the term reactant to generally refer to eithergas A or gas B, and will reserve the term precursor for referring to gasB. The applicability of these terms should be apparent from the contextto the skilled reader. The deposited compound mentioned above ispreferably an oxide or a nitride of the metal. There are severalprecursors of aluminum, gallium and other metals, such as silicon, zincand hafnium, available in the art that may utilized for this purpose.

As hinted above, a carrier gas may be used to bring low vapor pressurereagents/reactants/precursors such as liquids/solids into the ALD volumein lower portion 120 (see FIG. 2 and FIG. 6) via line 127. Explainedfurther, the liquid/solid reactant/precursor typically contained in abottle is first heated by a heater. Then, a carrier gas is used to carrythe heated/evaporated reactant from the bottle to the ALD volume. Theflow rate of the carrier gas may be adjusted as desired to control theintroduction of the reactant.

Another popular method involves using a bubbler mechanism. Morespecifically, a carrier gas is “bubbled” through the reactant while itis heated. This may be desired for really low vapor pressure reactants.The use of bubblers, heaters, carrier gases, pumps and other suchindustry standard techniques are well known to skilled artisans, andwill not be delved into detail in this specification. Preferably, thecarrier gas is nitrogen N2 or argon Ar because of their inert propertieswell known in the art.

Thus, gas B is pulsed into chamber 100 on a suitable carrier gas usingany of the above mentioned or sill other techniques. However, if it ishas a high enough vapor pressure then no carrier gas may be necessary tocarry it from its reservoir to chamber 100 through line 127. Referringto FIG. 6, once gas B is pulsed into line 127, it comes in contact withthe continuously present plasma excited/activated neutrals of gas A inthe ALD volume over heated substrate 140.

The two reactant gases (gas B and excited neutrals of gas A) and heatedsubstrate 140 react in a self-limiting manner. Without being limited toa specific theory, the self-limiting reaction may consist of a firstself-limiting reaction between the excited neutrals of gas A and heatedsubstrate surface 140. Note that this self-limiting reaction may also bereferred to as a surface-limited reaction or as a self-limiting surfacereaction because it ceases once all the reactive sites on the surfacehave been consumed by the excited neutrals.

Obviously when we refer to the reaction with the substrate, we arereferring to the upper or top surface of the wafer/substrate and not itsbottom surface which rests unexposed on the working surface of platenheater 142. It should be noted that unlike traditional art where onlyone reactant is present in the ALD volume at a time, the excitedneutrals of gas A in the present design are always present in the ALDvolume. This is because of the continuous production of the plasma fromthe continuous supply of gas A or plasma gas as explained above.

Again, without being limited to a particular theory, the firstself-limiting reaction is followed by a second self-limiting reaction.The second self-limiting (and surface-limited) reaction is between gas Band substrate surface 140 after its first self-limiting reaction above.The end-result of these self-limiting/surface-limited/surface-limitingreactions, also conveniently referred to as simply the self-limiting ALDreaction or the self-limiting reaction (in the singular), is anatomically sized film formed on the surface of substrate 140.

Additionally, there is no deposition on the walls of ALD volume,specifically lower portion 120. That is because their temperature iskept sufficiently below the temperature of substrate 140 to form thefilm by the above self-limiting reaction. Recall, that the walls oflower portion 120 are heated by cartridge heater(s) to avoid anycondensation of reactant gases. Using the above described design, theinstant technology is able to achieve films that are remarkably pure andhave uniform thickness, while avoiding damage to the substrate surfacefrom high energy plasma ions and electrons (plasma flux).

As already explained, the plasma in the instant design is rapidlyterminated, quenched, shorted or “killed” over the short distance/lengthbelow quartz plate 104E at metal plate 122A (see FIG. 6). In yet anotheraspect, the present design is unlike a typical chemical vapor deposition(CVD) system or other traditional ALD system designs which are dependenton the “flow” of reactants in the chamber. Without being limited by aspecific theory, the instant ALD techniques utilize activated neutralsfor its self-limiting or surface-limited reaction without requiringuniformity in gas distribution in the ALD volume.

As a result, the present design of metal plate 122A (and correspondingceramic plate 123A) requires much fewer holes 122B (and 123B) thanattributable to a typical dense holes showerhead design of theprevailing art. In a typical implementation, the instant design wouldrequire only 20-30 such holes in its metal plate as compared to hundredor more holes of a typical showerhead design. Once the monolayer of anatomically sized film is formed utilizing sufficient number of activatedspecies/neutrals, the remainder of the activated neutrals do not reactand are then pumped out.

Again, without being limited by a specific theory, the plasma, and morespecifically the plasma field, is quickly shorted/terminated/quenched bygrounded metal plate 122A, with minimal sputtering around metal holes122B. Preferably, metal plate 122A is made out of aluminum because ofits high conductivity in terminating the plasma as well as high thermalconductivity to be at a temperature equilibrium with the rest of chamber100. In other embodiments, stainless steel or copper may also beemployed. If plate 122A is made of stainless steel it will have bettersputtering qualities than aluminum, however one would need to contendwith its less efficient electrical and thermal conductivity thanaluminum. If a copper plate is employed, it would have superiorthermal/electrical conductivity but one would have to be careful aboutcopper impurities reaching the substrate.

As will be apparent by now, small holes 123B of ceramic plate 123A onlyallow the activated neutrals of gas A to pass through. They accomplishthis while also completely or almost completely or substantiallypreventing the flow of plasma flux containing energetic ions andelectrons to substrate 140. The present technology is able to do thisbecause holes 123B of ceramic plate 123A are specifically designed tohave diameter less than two Debye lengths of the plasma. Those skilledin the art will understand that Debye length A of a plasma is estimatedby:

$\begin{matrix}{{\lambda \simeq \sqrt{\frac{ɛ_{0}{kT}}{e^{2}n}}},} & {{Eq}\mspace{14mu} (1)}\end{matrix}$

where ε₀ is the permittivity of free space, k is the Boltzmann constant,e is the charge of an electron while T and n are the temperature anddensity of the plasma electrons respectively. Substituting the values ofconstants ε₀, k and e while ensuring the consistency of units in Eq. 1yields:

$\begin{matrix}{\lambda \simeq {\sqrt{\frac{{kT}\mspace{14mu} {in}\mspace{14mu} {eV}}{n\mspace{14mu} {in}\mspace{14mu} {cm}^{- 3}}}743\mspace{14mu} {{cm}.}}} & {{Eq}\mspace{14mu} (2)}\end{matrix}$

For a typical ALD recipe supported by the instant techniques, the plasmais powered at 200 Watts resulting in temperature T of around 2 eV withdensity n of about 10⁸ per cm³. Plugging these values in Eq. 2 resultsin:

λ≅√{square root over (2/10⁸)}743 cm≅0.105 cm≅1 mm  Eq (3).

Indeed, in the instant design the diameter of holes 123B of ceramicplate 123A is kept at 1 mm (or 0.038 inches) which is obviously lessthan 2×λ or 2×1.05=2.1 mm. The thickness of ceramic plate 122A itself isabout 6.35 mm (or 0.25 inches). This results in a large aspect ratio(thickness/diameter) of about 0.25/0.038≅6.58.

Let us consider the scenario that electron density n in the chamber weremuch higher than that used in Eq. 3, leading to a value of λ much lowerthan 1 mm. Without being limited by a specific theory, the value of nwould drop from the mouth of holes 123B at the surface of ceramic plate123A, towards the interior/deeper portion of holes 123B. This is evidentbecause the plasma neutrals will travel through holes 123B from theupper surface of ceramic plate 123A towards its lower surface,approaching substrate 140.

Because of the high aspect ratio of the ceramic plate of the instantdesign, at some point during this travel of the neutrals, the value of nwill drop sufficiently enough to achieve a value of λ close to thatcomputed in Eq. 3. Henceforth, the instant design is still able toachieve its benefits by ensuring that the diameter of ceramic plateholes 123B is kept less than 2×λ. Obviously, if the value of electrondensity n were any lower than that used in Eq. 3, that would onlyincrease the value of λ than that computed in Eq. 3.

As a direct consequence of the above design, there is anisolation/separation between the plasma and the ALD volumes. Thisisolation/separation is accorded by metal and ceramic plates 122A and123A respectively. Because of the smaller number of holes 122A and 123Athan traditional designs such as a grid, and the extremely small size ofholes 123B, the plasma volume and the ALD volume can be kept atdifferent desirable pressures.

The instant design allows one to maintain higher pressure in the plasmavolume than in the ALD volume. This consequently prevents precursor gasfrom diffusing to the plasma volume and depositing there. Therefore, inthe present design, quartz plate 104E does not accumulate deposits. Inthe preferred embodiment, the pressure in the ALD volume in lowerportion 120 is kept at 0.27 Torr or lower, while the pressure in theplasma volume/chamber is kept higher at 0.5 Torr. Moreover, the plasmacan thus be struck at a higher pressure where it is easier tocontrol/maintain and is more readily reproducible.

As compared to traditional art, gas A flows continuously into chamber100, and is always present around substrate 140 in an excited state.This is indeed a surprising aspect of the instant technology because bydefinition, traditional ALD techniques involve sending alternatingpulses of the reactants, but never the two reactants together. Incomparison, a cycle of the instant technology only involves sending onepulse of the precursor gas B in the continuous presence of activated gasA neutrals.

The design all the same still achieves the desired self-limiting ALDreaction. Then after steady-state/background pressure is achieved andany excess precursor and/or byproducts are removed, another pulse of gasB can be sent to repeat the cycle. As many cycles can be repeated asrequired to achieve a desired thickness of the film. The above resultsin a dramatic reduction of cycle-time of the instant technology totypically half of that of traditional art. This is illustrated in FIG. 7showing a timing diagram of the two gases/reactants A and B introducedin chamber 100.

Analogous to the prior art timing diagram shown in FIG. 1, each pulse PBof reactant/gas B in FIG. 7 corresponds to a duration of time T thatconsists of a dosing time and an additional wait time w as shown. Asplasma gas(es) or gas/reactant A with a background or operationalpressure are still flowing, during this time w, pulse PB decays to thebackground pressure. Wait time w may also thus be considered as thepurge time because during this time, any excess gas/reactant B and/orreaction products may be pump out or purged from the ALD volume. Anadvantage of a background or steady-state or operational pressureestablished by gas A independently of reactant/precursor gas B is thatit allows for a constant loading of turbomolecular pump 192 (see FIG.6). This in turn allows for a consequent stable pressure for plasmadischarge.

Note that while in FIG. 1, cycle-time is the sum of the time periodsT_(A) and T_(B) corresponding to pulses PA and PB of the twogases/reactants A and B respectively. In contrast, for the instanttechnology, as shown in FIG. 7, the cycle-time is equal only to the timeperiod T corresponding to pulse PB of the precursor or gas B whilereactant A is continuously present as shown by the horizontal line A.Moreover, since gas A is always present around substrate 140, notraditional purge cycle or dose-purge-dose-purge sequence is required inthe instant design. Specifically, the instant design only requirescycle-time of T consisting of a single dose-purge sequence. Note thatfor specific recipes, it may be possible to reduce instant wait time wvery significantly, approaching zero. To be complete, the dosing time inFIG. 7 for the instant design is obviously T-w.

The compact design of the instant technology with the exceptionalresults of film uniformity across the substrate surface, anddramatically reduced cycle-times, make it especially useful for avariety of applications. These applications especially include thosethat require high quality films at a high throughput. The technology isable to produce films of a variety of materials. The results from anon-exhaustive list of films of various materials deposited or coatedusing the instant continuous-flow plasma enhanced ALD (PEALD) techniquesare summarized below. The results indicate the high degree of uniformityof the film across a 6 inch diameter substrate. We refer to a film ofsuch a high degree of uniformity as a substantially uniform film.

-   -   1. Gallium nitride (GaN)        -   Precursor=GaCl3        -   Plasma N2 in standard cubic centimeters per minute (sccm)=20        -   Carrier N2 (sccm)=20        -   Substrate temperature (° C.)=400        -   Plasma RF power (Watts)=150        -   Precursor pulse time (ms)=60        -   Cycle-time (sec)=10        -   # of Cycles=150        -   Pressure in ALD volume (Torr)=0.09        -   Film thickness=244 Å (approximately 1.6 Å/cycle)        -   Thickness change across the surface=+/−0.3%    -   2. Aluminum nitride (AlN)        -   Precursor=TriMethylAlumium (TMA)        -   Plasma N2+H2            -   Plasma N2 (sccm)=50            -   Plasma H2 (sccm)=30        -   Carrier Ar (sccm)=50        -   Substrate temperature (° C.)=200        -   Plasma RF power (Watts)=200        -   Precursor pulse time (ms)=20        -   Cycle-time (sec)=5        -   # of Cycles=200        -   Pressure in ALD volume (Torr)=0.27        -   Film thickness=220 Å (approximately 1.1 Å/cycle)    -   3. Aluminum oxide (Al2O3)        -   Precursor=TMA        -   Plasma O2+Ar            -   Plasma O2 (sccm)=75            -   Plasma Ar (sccm)=5        -   Carrier Ar (sccm)=50        -   Substrate temperature (° C.)=200        -   Plasma RF power (Watts)=200        -   Precursor pulse time (ms)=60        -   Cycle-time (sec)=10        -   # of Cycles=200        -   Pressure in ALD volume (Torr)=0.27        -   Film thickness=530 Å (approximately 2.65 Å/cycle)        -   Thickness change across the surface=<1%    -   4. Gallium oxide (Ga2O3)        -   Precursor=Triethylgallium (TEGa)        -   Plasma O2+H2(sccm)            -   Plasma O2=10            -   Plasma H2=10        -   Carrier Ar (sccm)=20        -   Substrate temperature (° C.)=250        -   Plasma RF power (Watts)=150        -   Precursor pulse time (ms)=60        -   Cycle-time (sec)=5        -   # of Cycles=100        -   Pressure in ALD volume (Torr)=0.27        -   Film thickness=91 Å (approximately 0.91 Å/cycle)        -   Thickness change across the surface=<1%    -   5. Gallium oxide (Ga2O3)        -   Precursor=Triethylgallium (TEGa)        -   Plasma O2=10        -   Carrier Ar (sccm)=20        -   Substrate temperature (° C.)=250        -   Plasma RF power (Watts)=150        -   Precursor pulse time (ms)=60        -   Cycle-time (sec)=5        -   # of Cycles=150        -   Pressure in ALD volume (Torr)=0.19        -   Film thickness=180 Å (approximately 1.2 Å/cycle)        -   Thickness change across the surface=<1%

Note that in the above results, sometimes a single type of gas orchemical specie is employed for gas A or the plasma gas, while at othertimes multiple types of gases or chemical species are employed.Specifically, in recipes (1) and (5), GaN and Ga2O3 are produced usingan N2 plasma and an O2 plasma respectively. However, in recipes (2), (3)and (4), AlN, Al2O3 and Ga2O3 are produced using plasmas obtained fromgaseous mixtures of N2+H2, O2+Ar, and O2+H2 respectively. There are anumber of reasons/scenarios as to why multiple species of gas may beused to produce plasma in a given recipe. These include:

-   -   1. For stabilizing the plasma. This is the case in recipe (3)        above. In recipe (3), Ar at a low partial pressure is used to        stabilize the O2 plasma because O2 plasma is often difficult to        control otherwise.    -   2. Removing extra reaction byproducts such as carbon C. This is        the case in recipes (2), (3) and (4). This is because many        popular precursors of Al (for example, TMA) and Ga (for example,        TEGa) known in the art are carbon compounds. These compounds        produce extra/free carbon C as a byproduct of the self-limiting        ALD reaction. Therefore, in recipes (2) and (4), the excited        neutrals of H2 react with the extra carbon C to produce gaseous        compounds such as CH4 that can be easily removed from chamber        100. In recipe (3), the excited neutrals of O2 react with the        extra carbon C to produce CO2 which is then pumped away to        remove carbon from the process. In the absence of excited H2 and        O2, the extra carbon C would deposit as a solid on substrate        140, deteriorating the film thickness/quality and with the added        difficulty of removing the solid byproduct from the chamber.    -   3. For any necessary loading of turbomolecular pump 192 (see        FIG. 6). Sometimes a non-reactive gas may be added to gas A to        ensure that pump 192 has sufficient loading to operate properly.        More specifically, sometimes a recipe calls for keeping the        pressure of a gas in plasma volume to such a low pressure that        pump 192 would not operate effectively. In such a scenario, an        inert gas with sufficient partial pressure may be added such        that the total pressure of the gas mixture causes proper loading        of the turbo molecular pump 192.

It should be noted that in addition to gas A, another gas may also beadded to gas B. Recall that gas B is typically a metal precursor on acarrier gas. For example, an inert gas may also be added with thecarrier gas of the precursor to remove unwanted byproducts of thereaction as in scenario (2) above. Similarly, an inert gas may also bemixed with the carrier gas of the precursor to provide sufficientloading for turbo pump 192 as in scenario (3) above. In addition to theabove films, the instant techniques may be used to deposit many otherdifferent types of films. The various types of films deposited/coated bythe instant technology include AlN, Al2O3, GaN, Ga2O3, SiO2, Si3N4, ZnO,Zn3N2, HfO2, etc.

Before moving on, the reader should note that while there is no limit tothe number of individual species/types of gases or component gases thatmay be mixed to form gas A and gas B, care should be taken that thegases in the mixture are not very mutually reactive at the pressuresinvolved. In other words, an O2+H2 mixture for plasma at high pressureswill be mutually reactive. Note however that in recipe (4) above, it wasstill possible to use O2 and H2 but at the low pressures of 10 sccm,while the carrier for the precursor was Ar at 20 sccm.

FIG. 8 shows a schematic diagram of a gas supply system according to theinstant techniques. Specifically, FIG. 8 schematically shows upperportion 102 and lower portion 120 of chamber 100. FIG. 8 furtherschematically shows lines 126A to carry gas A and line 127 to carry gasB per earlier discussions to chamber 100. Recall that lines 126A arecarried from below chamber 100 and through its walls as shown by thedashed lines in FIG. 8 and then into upper portion 102 via line 106A asshown. To ensure uniformity of the reactant in upper portion 102,specifically in the plasma volume, gas A is supplied at two laterallyopposite gas feedthrough points 106B and 106C as shown. Alternatively,there may be a single gas feedthrough or more than two gas feedthroughs.The gas feedthrough(s) may also feed into upper portion 102 at any otherappropriate locations(s) such as on the sides of upper portion 102.

Recall from FIG. 3 that lines 126A consist of three individual gas linesthat can be used to carry various gas species into chamber 100 (see FIG.3). These gas species then mix together to come out in line 106A beforebeing delivered into upper portion 102. However, in alternatevariations, lines 126A can consist of just a single line, two lines ormore than three lines to carry any number of desired gases to upperportion 102 for a given implementation. FIG. 8 shows one practicalimplementation of the instant technology, and alternate variations notexplicitly shown or described are conceivable within the present scope.

Other componentry from earlier drawings is not explicitly shown in FIG.8 to avoid detraction from the main teachings provided herein. It isalso understood that in the schematic of FIG. 8, only one of a multipleof a given type of component may be marked by a reference numeral forclarity. For example, FIG. 8 shows five precursorreservoirs/bottles/bubblers 204 connected to five manual valves 210. Ofthese only one reservoir 204 and only one manual valve 210 is labeledfor clarity. Similarly, only one of five ALD valves 208 is indicated inFIG. 8, and so on.

FIG. 8 also shows four MFC's 202 filled with a hatched pattern goingfrom upper right to lower left, of various gas species as required toproduce gas A. For a typically recipe, only one or two of the fourreservoirs would supply gas A to chamber 100 as explained above. This isaccomplished by manipulating pneumatic valves 209, which are usuallycontrolled programmatically by a control software (not shown). Unliketraditional systems, pneumatic valve(s) 209 of the instantcontinuous-flow design do not need to be pulsed, and areactivated/opened at the start of the process. FIG. 8 also shows theinbound flow to MFC's 202 from below. This inflow is typically fed fromhigh pressure tanks from below (not shown) containing plasma gases,preferably N2, Ar, O2 and H2 per above teachings.

These gases are then carried to plasma source 104A in upper portion 102of chamber 100 via lines 126A and 106A as explained where they mixtogether. Then they are delivered as gas mixture A or more simply justgas A or the plasma gas to plasma source 104A. Plasma source 104Agenerates plasma from gas A whose excited neutrals then pass throughholes in metal and ceramic plates (not shown) to partake in aself-limiting reaction for ALD as already taught above.

Gas B typically containing a metal precursor is supplied into chamber100 by line 127. In the embodiment shown in FIG. 8, reactantinput/feeding line 129 is not used and is kept closed. Recall that gas Bis pulsed from reservoirs or bottles or bubblers 204 into the ALDvolume. This is accomplished via programmatic activation of one or moreALD valves 208 shown in FIG. 8.

The schematic of FIG. 8 also shows five manual valves 210 before ALDvalves 208. The manual valves are provided so bottles/bubblers 204 canbe conveniently replaced/refilled. In a typical ALD process, only one ofthe five manual valves 210 is kept open while only one of the five ALDvalves 208 is programmatically activated by a control software tointroduce the pulse of a precursor into chamber 100. However, in othervariations, as in the case of gas A, multiple gas species or componentgases may be supplied from reservoirs 204 via valves 208 and 210 to formgas mixture B or more simply just gas B. Gas B is then supplied tochamber 100 via line 127 to partake in the self-limiting ALD reaction asper the requirements of a given recipe.

FIG. 8 further shows MFC's 206 filled with hatched pattern going fromupper left to lower right. MFC's 206 are used to control the flow of oneor more carrier gases and have corresponding shutoff or on/off valves212. Per above discussion, a carrier gas is used to carry the typicallyliquid/solid heated precursor from reservoirs 204 into chamber 100. Theschematic of FIG. 8 also shows the inbound flow of the carrier gas toMFC's 206 from below. This inflow is typically fed from respective highpressure tanks of the carrier gas, preferably, N2 or Ar per abovediscussion. By controlling the various reagents/reactants using valves208, 209, 210, 212 afforded by the instant design shown in FIG. 8, it ispossible to change the composition of gas A and/or gas B during arecipe.

In other words, one or more of valves 209 controlling the flow of thecomponents of gas A from MFC's 202 can be programmatically manipulatedin a recipe to alter the composition of the plasma gas to chamber 100during the recipe. Similarly, one or more of valves 208 controlling theflow of the components of gas B from reservoirs 204 may beprogrammatically manipulated during a recipe to alter the composition ofgas B. This may also be done in conjunction with manipulating one ormore of valves 212 of carrier gases from MFC's 206. The abovefunctionality may be desired if compounds of more than one type need tobe deposited during the recipe. In this case, a purge cycle to cleanchamber 100 may be necessary once an ALD film of a required compound iscompleted and the next layer of the film of a different compound in thesame recipe needs to be deposited.

As already mentioned that FIG. 8 provides one useful implementationwhile alternative gas supply designs may also be envisioned within thepresent scope of the disclosed techniques. Indeed, in another usefulembodiment, a variation of the schematic of FIG. 8 is used to supportthermal ALD processes. This variation is shown in FIG. 9. In FIG. 9,there are two additional reservoirs 214A and 214B for providingcontinuously flowing reactant for thermal oxidation via line 129 tolower portion 120 of chamber 100. Lines 126A are no longer used becauseplasma is not used for activation of neutrals. Instead, heat is used tohelp dissociate the reactant species for their reaction on the heatedsurface of substrate 140.

In one such thermal ALD variation, heated and externally supplied ozone(O3) from an ozone generator 214A is sent to the ALD volume. As shown,generator 214A is connected to a manual valve 210 for any convenientremoval/replacement operation. Alternatively, thermally excited watervapor from reservoir 214B is sent to the ALD volume for thermaloxidation. In still other variations, nitric oxide (NO) supplied from atank (not shown) may be used as an oxidizer instead of ozone or watervapor. In any case, water vapor, O3 or NO supplies are controlled by ALDvalves 208 for programmatic introduction into the ALD volume. Suchembodiments may preferably be used to produce oxide films such as Al2O3,Ga2O3, etc.

In yet another thermal ALD variation of the present design, nitridefilms taught earlier may also be produced. Nitridation is accomplishedby flowing ammonia NH3 or hydrazine from reservoir 216 via micrometervalve 218 into the ALD volume of chamber 100 as shown in FIG. 9. Thisvariation may be used to deposit nitride films including AlN and GaN.However, in such a thermal ALD process, the free hydrogen as a productof the reaction may result in hydrogen content in the deposited film.This may cause the film stoichiometry to deteriorate as compared toearlier plasma enhanced ALD embodiments. Moreover, the excessammonia/hydrazine also needs to be abated through potentially expensiveabatement techniques known in the art.

It should be remarked that the above explained thermal ALD embodimentssupported by the instant design are not continuous-flow. In other words,both the precursor as well as the oxidizing/nitriding reactants arepulsed alternately in a typical dose-purge-dose-purge sequence. Asalready explained, that plasma is not used for reactant activation inthese thermal embodiments. As such, continuously flowing plasma gas A inlines 126A of earlier PEALD embodiments is not used. The purpose ofproviding these thermal embodiments is to show that the instantcontinuous-flow PEALD design is versatile enough to support moretraditional thermal ALD processes also.

However, the above thermal ALD embodiments still benefit from thecompact design of the smaller ALD volume of the earlier PEALDembodiments. Even though no plasma is used in these embodiments,cycle-time is still reduced, because a smaller chamber volume needs tobe purged than traditional thermal ALD systems. Though the presentdesign fully supports thermal ALD as explained above, the plasmaenhanced embodiments explained earlier have shown to produce veryuniform and high quality films without downstream abatement processes.

Let us now turn our attention to an advantageous post processing step ofthe present techniques. This step prevents oxidation of the hotsubstrate sample after film deposition from the above appliedtechniques. Specifically, the step utilizes a load-lock mechanism withan automatic/robotic arm and an end effector. In conjunction with a liftassembly of platen heater 142 (see FIG. 4), the end effector transfersthe substrate after film deposition from the ALD volume to an airtightload-lock compartment. The compartment contains inert N2 in which thesubstrate is allowed to cool off before being exposed to the atmosphere.Otherwise, if the hot substrate were to be exposed to the atmosphere, itwould oxidize/react with the atmospheric oxygen and this oxidation wouldnegatively affect the quality of the deposited film.

To understand the working of this post processing step in detail, let uslook at a right isometric view of the embodiment illustrated in FIG. 10.FIG. 10 shows chamber 100 of the earlier embodiments (see FIG. 2-6)without the reference numerals for all of the components for clarity ofillustration. In particular, FIG. 10 shows a load lock mechanism 150interfaced/connected with lower portion 120 of chamber 100. A roboticarm with an end effector inside load-lock 150 automatically transfersthe finished substrate 140 from chamber 100 to its airtight compartment.In that compartment, substrate 140 would cool off to room temperaturewithout being exposed to environmental oxygen.

To visualize this further, let us look at the detailed view of load-lockmechanism or assembly 150 in FIG. 11. FIG. 11 shows a load-lockcompartment 160 whose top and front walls have been removed from thefigure to delineate the internal components. In addition to compartment160 there is a flap door 152 preferably made out of polycarbonatethermoplastic or some other suitable material capable of sustaining theoperating temperature and pressure conditions of the system. FIG. 11further shows flap door actuators 154 that are used to programmaticallyopen or close flap door 152 of load-lock compartment 160. Compartment160 attains a sealed state when flap door 152 is in the closed position.

There is a robotic arm or simply arm 156 with an end effector 158 asshown in FIG. 11. Let us first refer to FIG. 4 to review lift assembly143A-C of platen heater 142 introduced earlier. Specifically, actuator143C and actuator mount 143B are first programmatically activated toraise sample lift 143A to the raised position shown in FIG. 4. Lift 143Ain turn raises the hot substrate above its top or working surface. Nowreferring to FIG. 11 again, arm 156 and end effector 158 are used tomove underneath substrate 140 raised above platen heater 142 and to propand carry substrate 140 into compartment 160 of load-lockmechanism/assembly 150.

To linearly manipulate arm 156 and end effector 158 a ballscrew assembly162 (whose threads are not visible in FIG. 6) is provided. Ballscrewassembly 162 is activated by a vacuum rotational feedthrough 166 drivenby a stepper motor 168. Stepper motor 168 in conjunction with rotationalfeedthrough 166 and ballscrew assembly 162 are used to programmaticallydrive arm 156 with end effector 158 along guide rail 164 in and out ofcompartment 160.

During normal operational flap door 152 is kept in a closed position andvacuum conditions are achieved in compartment 160 by a load-lock vacuumpump (not shown) connected via connections 172. Connections 172 are thenused to fill load-lock compartment 160 with N2. Connections 172 includeconnections/pipes for pumping, venting, filling and feedthrough gaugeconnections for load-lock mechanism 150. Once ALD process is finished inchamber 100, substrate 140 is then brought into the airtight inert N2environment of compartment 160 per above explanation. It remains therewith flap door 152 closed until it cools off to room temperature. Thisminimizes any oxidation and deterioration of its surface.

FIG. 12 shows in a flowchart form the steps required to carry out anexemplary embodiment of the continuous-flow plasma enhanced ALD (PEALD)techniques described herein. In conjunction with FIG. 2-11 andassociated explanations, flowchart 300 of FIG. 12 depicts that theprocess starts by sealing chamber 100, and specifically closing itsupper portion 102 and lower portion 120. This step is shown by processbox 302. Then next step 304 is carried out by heating substrate 140 bypowering platen heater 142. In parallel, gas A or the plasma gas iscontinuously flowed into chamber 100 per above explanation as indicatedby box 306.

Next, planar ICP source 104A is powered as shown by box 308. Morespecifically, in step 308 electrical power to the power supply of ICPsource 104A is turned on and appropriate power setting is selected toproduce RF signal of the desired strength. This RF signal is carried toICP source 104A, specifically its RF antenna/coil 104B via RF input port104C. In one embodiment, the antenna/coil can be powered at up to 1000watts.

Next, gas B is pulsed into chamber 100, as indicated by box 310. Thisstep is accomplished by utilizing fast ALD valves 208 (see FIG. 8-9)with actuation times preferably less than 100 milliseconds. As a result,excited neutrals of gas A, the pulse of gas B and heated substrate 140react in a self-limiting manner taught above to produce an atomicallysized film on substrate 140. One cycle of the process constitutessending the pulse and waiting enough time for the pulse to decay to thebackground or steady-state pressure of the chamber per aboveexplanation.

As already explained, any excess precursor or gas B as well as anyreaction byproducts may also be purged during this wait/purge timeindicated by process box 312 in FIG. 12. The cycle-time is equal to theduration of sending the pulse (dosing) and the wait time w (also seeFIG. 7 and associated explanation). Alternatively stated, the cycle-timeis equal to the time between the initiation of the pulse and the end ofwait time w (which coincides with the initiation of the next pulse).Still differently put, the cycle-time is equal to the time between theinitiation of each pulse. The cycle is repeated as many times as neededto obtain a desired thickness of the film on the surface of substrate140 as shown by the Repeat loop 318.

Once film deposition is complete, load-lock mechanism 150 is activatedto bring sample/substrate 140 from chamber 100 into the inert conditionsof compartment 160 as depicted by process box 314. Finished substrate140 then cools off in compartment 160 of load-lock 150 to the ambientroom temperature as indicated by box 316. Note that in alternativeembodiments, the order of the above steps may be varied while adheringto the principles taught herein. For example, steps 304, 306, 308, 310may all be carried out in parallel. In such a scenario, theself-limiting ALD reaction will only properly occur once substrate 140is at its desired temperature and the plasma with the desired strengthhas been generated according to the recipe. Similarly, one canconceivably perform step 302 in parallel with steps 304 and 306. Othervariations of the order of the steps may also be conceived within thepresent scope.

FIG. 13 shows a screenshot from the control software introduced abovethat is used to control/manipulate the instant ALD system design forexecuting a recipe. Specifically, screenshot 350 of FIG. 13 shows apressure chart 352A indicating pressure versus time. The pressurereadout can be selected from toggle button 352B to either general systempressure measured by a wide range gauge (WRG), or ALD volume or processchamber pressure measured by a Pirani gauge. There are several choicesof instruments available from vendors for these gauges to the skilledartisans. These include WRG-D gauge from Edwards for the WRG gaugeabove, APGX series linear convection gauge from Edwards for the Piranigauge above. Additionally, load-lock pressure is monitored by amicro-Pirani gauge such as HPS Series 925 MicroPirani gauge from MKSInstruments.

Screenshot 150 of FIG. 13 further shows a recipe table 354 where theuser can write a set of instructions to be executed for the recipe. Theinstruction set can be saved, edited, loaded, etc. In addition toprogrammatic controls of ALD valves (see FIG. 8-9), every manual controlis also available as a recipe instruction. The instructions include thefollowing:

-   -   1. Pulse—for opening ALD valve for the specified pulse duration.    -   2. Wait—for waiting specified number of seconds before executing        the next instruction.    -   3. Jump To—for jumping to a specified instruction and        repeating/looping a specified number of times. This capability        is crucial for repeating cycles in order to obtain film of        required thickness (also see FIG. 2-6 and FIG. 12 and the        associated explanation).    -   4. Heater—for changing the temperature setpoint for the selected        heater. A setpoint is an operator defined value and the heater        would continue heating until this setpoint is achieved and then        maintain the setpoint temperature thereafter.    -   5. Thermalize—for waiting until the temperature setpoint for the        selected heater above is reached.    -   6. Gas Flow—for controlling the flow of gases for the selected        MFC's (see also FIG. 8-9 and associated explanation).    -   7. Angle Valve—for opening or closing pump valves for longer        precursor dwell/residence times in high aspect ratio (HAR)        deposition applications. Note that for HAR applications turbo        192 can be slowed down to increase the dwell/residence times of        the precursor.    -   8. RF—for delivering selected RF power to ICP source 104A.    -   9. Turbo—for turning on or off turbomolecular pump 192 (see FIG.        6 and associated explanation).    -   10. Regulate pressure—for automatically maintaining the selected        pressure at the specified pressure setpoint.

Screenshot 350 of the control software of the present design furthershows gauge 356 indicating the speed of the turbo pump as a percentageof its maximum speed. It also shows gauges 358 that include turbo speedin Hertz and a turbo setpoint indicator, as well as readouts from WRGand Pirani pressure gauges per above explanation. In the lower region ofthe screen indicated by reference numeral 360 are status bars of variouscomponents and sub-systems, including cooling subsystem, compressed dryair (CDA), venting status of the chamber, RF status, etc.

Further shown are MFC controls 362 showing which gases are being flowedat what pressure, RF controls 364 and pressure controls 366. Also shownare various temperature setpoints and corresponding readings 368. Theseinclude the temperature setpoints and current temperature readings forplaten sample heater 142 (see FIG. 4 and FIG. 6), chamber 100, turbopump 192, reservoirs/cylinders 202, 204, 206 (see FIG. 8) and 214A-B and216 (see FIG. 9), and valves/lines, etc. as shown. Finally, screenshot350 also shows an MFC configuration menu 370 where the user can specifywhich gases are actually (physically) connected to which MFC's in thesystem.

For completeness, FIG. 14 shows screenshot 380 of the control softwareof the instant design from an actual recipe depositing a GaN film usingGaCl3 as the precursor. While most of reference labels from FIG. 13 areomitted in FIG. 14 to avoid repetition, the reader is encouraged tonotice the pulse train of precursor GaCl3 as shown in pressure chartsection 352A of screenshot 380. The reader will notice that after thespike or dosing of each pulse is the wait time w per above explanationindicated by the pressure trail following the spike. During this time w,the pressure decays to background/steady-state levels and any unwantedreactants/products are removed (also see FIG. 6-7 and associatedexplanation).

It should again be noted that the structure and configuration of thevarious embodiments described thus far is by way of example only.Alternative structures and configurations are entirely conceivablewithin the present scope. In particular, the present design requires theplasma generated by an ICP source to be separated or isolated from theALD volume by above taught combination of metal and ceramic plates withtheir corresponding holes. This is to allow excited neutrals from theplasma gas to pass through the plates without allowing the plasma fluxto enter the ALD volume and from damaging the substrate. As an addedadvantage, such a design allows one to maintain a pressure differentialbetween the plasma volume and the ALD volume as taught above.

Therefore, in alternative embodiments, there may not be an upper andlower portion of the chamber, or the chamber may have more than twosections/portions. Similarly, gases may be supplied to the chamber inalternative fashion. This includes feeding gases in from the sides andvia any number of appropriate gas feedthroughs. All such variations maybe feasible so long as the plasma is kept above the conducting metalplate, and the precursor gas is kept below the ceramic plate in order tomaintain the above discussed separation/isolation. More specifically,the separation/isolation objective is achieved by feeding plasma gas tothe ICP source above the conducting metal plate, and by feeding theprecursor gas to the chamber below the ceramic plate. Still otherconfigurations may be conceived by those skilled in the art.

The teachings heretofore have been focused on disclosing the methods andsystems for the instant continuous-flow ALD techniques for a singlesubstrate/wafer configuration. This is obvious, because the aboveembodiments produce a uniform thickness film on a single substrate/wafer140 (see FIG. 2-6 and FIG. 8-14). However, in a batch version of theinstant design, selected components of earlier embodiments are utilizedto incorporate multiple wafer substrates on which the highly uniformfilm is deposited simultaneously according to above taught techniques.

The schematic illustration of such an embodiment 400 is provided in FIG.15. The reader will notice that FIG. 15 incorporates many componentsfrom the earlier single-wafer schematics of FIG. 8-9. However, in batchPEALD embodiment 400, the plasma is generated by a remote plasma source404A. The plasma gases are supplied to remote plasma source 404A as inearlier single-wafer embodiment, from MFC's 202 and valves 209.Preferably, plasma source 404A is an inductive plasma source. Moreover,plasma source 404A may or may not be a planar plasma source. This isbecause its form factor no longer needs to conform to chamber 100 of theearlier described single-wafer designs. At or new plasma source 404A aregrounded metal plate and ceramic plate of the earlier embodiments asshown by dashed lines in plasma filter module 404B.

As per above teachings, the plasma is terminated by the grounded metalplate in filter module 404B and then filtered through the small holes ofthe ceramic plate in filter module 404B. Activated neutrals of theplasma are then carried from plasma filter module 404B via normalstainless steel tubing 406 to a batch chamber 402 as shown. According tothis aspect of the technology, the activated neutrals will stay excitedfor a reasonable tubing distance 406, preferably about half a meter. Theplasma is then delivered to batch chamber 402.

Batch chamber 402 comprises several identical substrate modules of whichone substrate module is marked by reference label 414. Substrate modulesare vertically stacked in batch chamber 402 as shown. Each substratemodule 414 comprises a heated wafer 140. In one variation, substratemodules 414 have quartz housing and substrates 140 are heated byInfrared (IR) lamps (not shown). Note that other appropriate waferheating mechanism(s), resistive or otherwise, such as platen heaters mayalso be used as will be appreciated by skilled artisans. Such heatingmechanisms are omitted from FIG. 15 to avoid detractions from the mainteachings of the present embodiments.

As in single-wafer embodiments, precursor bottles 204, valves, 210 and208, and carrier gases from MFC's 206 and on/off valves 212 are used tosupply ALD precursor for the above taught self-limiting reaction inchamber 402. As shown, the precursor is supplied via line 408 directlyabove substrates 140 in the ALD volumes inside substrate modules 414.There, the plasma activated neutrals come in contact with the precursordelivered by line 408 above heated substrates 140. The resultingself-limiting reactions deposit an atomically sized film on allsubstrates 140 simultaneously as a product of the reaction in this batchoperation. As before, as many ALD cycles may be run and pulses of gas Bmay be passed in batch chamber 402 in order to obtain ALD films of thedesired thickness.

During the ALD cycles, gases from ALD volumes are pumped out via exhaustline 410. Any remaining gases in chamber 402 may be pumped out viaexhaust line 412. In this manner, as in the case of single-waferembodiments, pure and extremely uniform ALD films are simultaneouslyproduced on all substrates 140 in substrate modules 414. Substrates 140are then preferably allowed to cool off in the clean, inert environmentof chamber 402 to lower operating or room/ambient temperature. As inearlier embodiments, this post-processing step is necessary in order toprevent/minimize oxidation of the wafers by environmental oxygen. Notethat in this batch embodiment, load-lock mechanism 150 (see FIG. 10-11)from single-wafer embodiments is not used.

However, in a cluster version of the instant technology, each substratemodule is a single-wafer processing chamber of the earlier single-waferembodiments. Each chamber has its own load-lock mechanism and a roboticarm for loading/unloading the wafers. Then a whole cluster of wafers maybe coated simultaneously according to the instant techniques. As withthe single-wafer embodiments, other configurations supportingdeposition/coating of multiple wafers within the present scope may beconceived by those skilled in the art. Such configurations may includebatch/cluster variations or still other ways of organizing and coatingmultiple wafers according to the instant principles.

As already taught above, heating of the substrate can be done byInfrared radiation (IR). This mechanism eliminates/reduces plate contactand results in a more uniform substrate temperature. In othervariations, for surface cleaning prior to starting the ALD process, thesubstrate can be biased with RF. Specifically, plasma can be producedaround the wafer/substrate to remove any organic contaminations beforecommencing the ALD process. This also improves adhesion of the substrateto the plate.

Still other variations of the present technology include double-sidedALD. In other words, the technology may be adapted to coat both sides ofthe wafer/substrate. As already mentioned, the present technology mayalso be used to deposit oxides such as hafnium(IV) oxide (HfO2), thatare promising for the development of next-generation logic.Additionally, by modifying various components, the present technologymay also be used to carry out ALD of graphene.

In view of the above teaching, a person skilled in the art willrecognize that the apparatus and methods of invention can be embodied inmany different ways in addition to those described without departingfrom the principles of the invention. Therefore, the scope of theinvention should be judged in view of the appended claims and theirlegal equivalents.

What is claimed is:
 1. An atomic layer deposition (ALD) systemcomprising: (a) a cylindrical chamber comprising an upper portion and alower portion such that said upper portion and said lower portion areclosed to obtain a sealed state of said chamber; (b) said upper portioncomprising a planar inductively coupled plasma (ICP) source laterallyaffixed at its distal end from said lower portion; (c) a substrateplaced atop a platen in said lower portion and heated by a platen heaterto a desired temperature; (d) said substrate isolated from said ICPsource in said chamber by a grounded metal plate laterally affixed abovesaid substrate and a ceramic plate laterally affixed below said groundedmetal plate but above said substrate, said grounded metal plate and saidceramic plate having a first plurality of holes and a second pluralityof holes respectively such that each of said first plurality of holes isaligned with a corresponding hole of said second plurality of holes, andeach of said second plurality of holes having a diameter less than twoDebye lengths of a plasma continuously generated above said groundedmetal plate from a gas A by said ICP source; (e) said gas A continuouslydelivered to said ICP source and said plasma terminated by said groundedmetal plate; (f) a pulse of a gas B passed into said chamber from belowsaid ceramic plate; (g) each of said gas A and said gas B comprising oneor more individual chemical species; wherein excited neutrals of saidgas A, said gas B and said substrate react in a self-limiting manner toproduce a uniform atomically sized film on said substrate.
 2. The systemof claim 1, wherein said excited neutrals of said gas A pass throughsaid first plurality of holes and through said second plurality of holesto reach said substrate.
 3. The system of claim 1, wherein one of saidone or more individual chemical species of said gas B is a carrier gas.4. The system of claim 3, wherein said element (f) is repeated two ormore times to produce multiple layers of said uniform atomically sizedfilm on said substrate.
 5. The system of claim 4 wherein said multiplelayers are composed of a compound selected from the group consisting ofaluminum nitride (AlN), aluminum oxide (Al2O3), gallium nitride (GaN),gallium oxide (Ga2O3), silicon oxide (SiO2), silicon nitride (Si3N4),zinc oxide (ZnO), zinc nitride (Zn3N2) and hafnium oxide (HfO2).
 6. Thesystem of claim 5 further comprising a load-lock mechanism forminimizing oxidation of said substrate after said multiple layers havebeen produced.
 7. The system of claim 6 wherein the length of the plasmavolume is approximately one inch and the transit distance is less thanone centimeter.